The studies outlined in this proposal are an extension of our original observation that cyanate inhibits the sickling of erythrocytes in vitro. While the evidence to date favors the idea that it is the increased oxygen affinity of carbamylated HbS that inhibits cell sickling, further studies under physiological conditions are needed. We plan to approach this question through studies on hybrid hemoglobin S tetramers carbamylated on specific chains; we have recently worked out a more direct method for the preparation of these derivatives. The effects of CO2 and 2,3-DPG on the gelling properites of alpha sub 2C beta sub 2 and alpha sub 2 beta sub 2C will be compared. An attempt will be made to incorporate the C14- labelled hybrids into animal cells by the technique of "exchange loading"; the survival of the cells in vivo will then be monitored in the animals. Other chemical modifications of the NH2-terminal residues of HbS will be undertaken and we shall determine the effects of such modification on the oxygen affinity and gelling properties of HbS. Enzymic removal of residues from the NH2-terminal end of the molecule and the replacement of these residues by adsorption with peptides of varying sequence may give some answers on the basic chemical reason for the relative insolubility of deoxy HbS. With the assay that we have developed for the determination of free cyanate in whole blood, we will investigate different routes of administration and various capsule coatings in order to attain the maximum amount of hemoglobin carbamylation for a given amount of sodium cyanate. Peptide mapping of the Hb chains prepared from the blood of "benign" sicklers will be undertaken. Studies on the optical rotatory dispersion and circular dichroic properties of HbS will be initiated.